1. Field of the Invention
The present invention generally relates to a taut, torsional flexure and a compact drive for, and a method of, scanning light using the flexure, especially for use in a color image projection arrangement operative for projecting a two-dimensional image in color while maintaining low power consumption, high resolution, miniature compact size, quiet operation and minimal vibration.
2. Description of the Related Art
It is generally known to project a two-dimensional image on a screen based on a pair of scan mirrors which oscillate by respective drives in mutually orthogonal directions to scan a laser beam over a raster pattern. However, the known image projection arrangements project the image with limited resolution, typically less than a fourth of video-graphics-array (VGA) quality of 640×480 pixels, consume a relatively large amount of electrical power, and are relatively heavy in weight and occupy a relatively large volume, thereby rendering them impractical for use in miniature, hand-held, battery-operated applications.
For example, the drive for one of the scan mirrors includes a permanent magnet jointly movable with the mirror. The magnet and the mirror are mounted on a flexure that permits oscillation about an axis. An electromagnetic coil is energized by a periodic drive signal and generates an electromagnetic field which interacts with the permanent field of the magnet to flex the flexure and cause the magnet and, in turn, the scan mirror to oscillate about the axis.
Although generally satisfactory for its intended purpose, the above-described electromagnetic drive is not ideal for miniature, hand-held, battery-operated applications. For example, the flexure must be tensioned to a taut state to better withstand ambient temperature changes and to produce repeatable oscillations. Such tensioning is provided by additional discrete components, such as clamps, pins and screws, all of which increase the weight, volume and energy expenditure of the drive. In addition, the assembly of these additional components increases the cost and complexity of manufacture of the drive, as well as increasing the likelihood that one or more of these additional components will become loose or fail, thereby compromising the tension on the flexure and eventually leading to unreliable, unrepeatable, temperature-dependent scanning. A laser beam, for example, incident on the mirror supported by such a compromised flexure will not be accurately directed to its intended pixel of the image and, as a result, the resolution of the projected image is degraded.